- must、can't、should、might/may/could 全部能翻成中文的「可能」，但确定程度天差地别，从「很确定」一路排到「一般可能性」逐一整理。
- must 表示根据证据推理出的结论，can't 表示很确定不可能；be bound to 虽不是情态动词，但同样表达确定的预测。
- ⚠️ should/shouldn't 隐含「一切顺利」的意思，不能用来预测负面结果；can 不能谈具体事件的可能性，这个意思要换成 may/might/could。
- 学完能更精确地表达「我很确定」「应该会」「有可能」这几种不同把握程度。
重点内容
确定（Certainty）：must
用 must 表示很确定某事是真的，或认为这是唯一合理的可能：
- You must be tired. You've been travelling all day.
- That must be Clare's house. I can see her car outside.
must 表示这是推理得出的结论（看证据/逻辑推断），不是单纯陈述事实：
- This must be her house.（根据证据推理）
- This is her house.（单纯陈述事实）
be bound to（表确定的猜测/预测）
不是情态动词，但用法相关：
- There are transport strikes tomorrow, so travel is bound to be more difficult.
- They are by far the best team – they're bound to win.
确定：can't
表示很确定某事不可能：
- That can't be right, can it?
- It can't be easy for him, looking after three kids on his own.
不太确定：should/shouldn't
表示「预期会这样」，因为这是正常/合理的期待：
- Rest and drink plenty of water. You should feel better in a day or two.
should/shouldn't 隐含「如果一切顺利」的意思——⚠️ 不能用来预测负面/不想要的结果：
- ❌ The treatment should be very painful. ❌ Our flight shouldn't arrive on time.
不太确定：might、may、could
表示认为现在/未来某事有可能，但不确定：
- I might see you tomorrow if you're in the office.
- There may be another issue that we don't know about.
- This illness could be prevented.
三者意思相同，但 may 比 might/could 更正式。
情态动词后面加 well，可以让可能性听起来更高：
- I'll try the pharmacy, but it might well be closed now.
- She may well have to rethink her plan.
否定形式是 may not 和 might not（mightn't）——表示「可能不」；⚠️ couldn't 不一样，couldn't 表示「不可能」，比 may not/might not 语气强得多。
一般可能性：can
can 不用来谈某个具体事件/情况的可能性：
- ❌ Azi can be in the garden.
- ✅ 应改用 may/might/could：Azi may/might/could be in the garden.
can 用来表示「有时会发生」或「有能力发生」：
- Noisy neighbours can be a problem if you're living in a flat.
- It can be very cold here in winter.
所有情态动词后面接不带 to 的不定式（原形动词）。
例句练习
| 英文 | 中文 |
|---|---|
| She might well be on the train. | 她很可能在火车上。 |
| That must be his dad. | 那一定是他爸爸。 |
| That can't be right. | 那不可能是对的。 |
| You're bound to make mistakes occasionally. | 你偶尔难免会犯错。 |
常见错误
❌ Azi can be in the garden.（想表达具体情况的可能性）
✅ Azi may/might/could be in the garden.
can 不能用来谈论某个具体事件是否可能，这个意思要用 may/might/could。
❌ Our flight shouldn't arrive on time.（用 should 预测负面结果）
✅ 直接说 The flight might be delayed. 或改变说法，避免用 should/shouldn't 预测不想要的结果。
should/shouldn't 只用在「一切顺利、合理预期」的正面语境，不适合预测负面结果。
Sources
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